Add Neo4j integration tests and query rate-limiting logic

Introduce comprehensive integration tests for Neo4j bug fixes covering batching, event relationships, and processing logic. Add rate-limiting to Neo4j queries using semaphores and retry policies to prevent authentication rate limiting and connection exhaustion, ensuring system stability under load.

pkg/neo4j/hex_utils_test.go

@@ -74,6 +74,11 @@ func TestNormalizePubkeyHex(t *testing.T) {
 			input:    binaryEncoded,
 			expected: "0000000000000000000000000000000000000000000000000000000000000001",
 		},
+		{
+			name:     "Raw 32-byte binary to hex",
+			input:    testBytes,
+			expected: "0000000000000000000000000000000000000000000000000000000000000001",
+		},
 		{
 			name:     "Lowercase hex passthrough",
 			input:    []byte("0000000000000000000000000000000000000000000000000000000000000001"),